Bgp Bestpath Med - Allied Telesis SwitchBlade x908 Series Software Reference Manual

BGP Commands

bgp bestpath med

This command controls how the Multi Exit Discriminator (MED) attribute comparison is
performed. The bgp bestpath med command features the confed and missing-as-worst
parameters relating to MED comparison.
The confed parameter enables MED comparison among paths learned from confederation
peers. The MED attributes are compared only if there is no external AS (Autonomous System),
where an external AS is one that is not within the confederation. If there is an external AS in
the path, then the MED comparison is not made.
For example, in the following paths the MED value is not compared with Path3 since it is not
in the confederation. MED is compared for Path1 and Path2 only.
Path1 = 32000 32004, med=4
Path2 = 32001 32004, med=2
Path3 = 32003 1, med=1
The effect of the missing-as-worst parameter is to treat a missing MED attribute in a path as
having a value of infinity, making the path without a MED value the least desirable path. If the
missing-as-worst parameter is not configured, the missing MED attribute is assigned the
value of 0, making the path with the missing MED attribute the best path.
Use the no bgp bestpath med command to prevent BGP from considering the MED
attribute when comparing paths.
Syntax
bgp bestpath med {[confed] [missing-as-worst]}
Parameter
confed
missing-as-worst
Router mode
Mode
Example
awplus(config-router)#
awplus(config-router)#
awplus(config-router)#
bgp always-compare-med
Related Commands
bgp bestpath as-path ignore
bgp deterministic-med
38.10
Description
Compares MED among confederation paths
Treats missing MED as the least preferred one
awplus# configure terminal
awplus(config)# router bgp 100
bgp bestpath med missing-as-worst
awplus# configure terminal
awplus(config)# router bgp 100
bgp bestpath med confed
awplus# configure terminal
awplus(config)# router bgp 100
bgp bestpath med confed missing-as-worst
Software Reference for SwitchBlade® x908, x900 and x600 Series Switches
TM
AlliedWare Plus Operating System - Software Version 5.3.1 C613-50007-01 REV B